Ask a dozen engineers how to make great vocal recordings and you'll get a dozen different answers — but there are some ground rules, as Hugh Robjohns explains.
The most certain thing you can say about vocals for a song is that they will invariably be heard above all other elements of the track. Consequently, any imperfections in the equipment used, the recording, or the performance will tend to be pretty obvious. To make matters even worse, everyone knows what a voice is supposed to sound like, so inappropriate equalisation, excessive sibilance, or unexpected changes in quality through the song will be immediately recognisable.
The golden rule is that old one about silk purses and sows' ears: no microphone, EQ, or compressor can cure bad vocal technique. The usual problems are poor breath timing, noisy breaths and unintelligible diction; a few sessions with a decent voice or singing coach can make dramatic improvements in a very short space of time, and it is well worth encouraging a budding vocalist to take some professional instruction.
Your first decision is whether to record the vocals 'live', with the rest of the band playing, or to overdub a clean vocal track after the instrumentation has been laid down (although it is usual to record a guide vocal with the basic instrumentation early on in the session). As recording a vocal track as an overdub process is the only way to achieve the kind of sound quality that most listeners will expect, this is the method I'll be concentrating on.
Timing And Location
One of the most important aspects of getting a great vocal sound has nothing at all to do with the technology. The best microphone technique in the world cannot turn a lacklustre performance into a good one, and there is no point in recording anything but the very best. A lot of factors influence performance, some of them physical, some psychological, but timing is probably one of the most important.
Apart from the guide line recorded at the start of a session, recording the vocals is usually left to the very end of the recording process, when everything else has been recorded, replaced, overdubbed and polished. At the end of a long day, possibly in a smoky atmosphere, suffering the drying effects of air conditioning, with everyone a little tense or sensitive from 'exchanges of artistic temperament', may not be the best time in the world to coax the ultimate performance from your singer. On the other hand, first thing in the morning may not be much better. This is where the producers's role becomes so important — it's a case of judging when the vocalist's enthusiasm and motivation are at their highest, when their voice is in peak condition, and when there is enough of the song's instrumentation already laid down to enable a vocal line to be added. Similarly, it is important to be able to decide when the best has been achieved, or when to try another take.
The recording location can also have a significant effect on the quality of the end result: no one is going to perform well in a dreary room with bright fluorescent lighting. Some singers like to perform on their own in a dimly lit room, others prefer a brighter setting or want to feel the support of their fellow musicians in the studio with them.
Eye‑contact between the producer, engineer and vocalist is very important — it is surprising what encouragement can be passed in the wink of an eye or a well‑timed smile. On the other hand, an automatic facial expression reacting to something the singer cannot see in the control room might have disastrous effects, so you'll have to figure out the best way to extract the perfect performance from a particular vocalist. It's definitely worth avoiding a dozen gawping faces staring at the vocalist through the control room window, though, so try to get the band to go away while you are tracking the vocals.
It is currently fashionable to record many of the electronic or electro‑acoustic instruments in the control room and some engineers expand this practice to include the vocals. The practicalities of such a technique will depend largely on the size, acoustics and noise levels of the control room, but it can improve the bond between producer or engineer and singer to be all the same side of the glass. I am not a fan of this technique myself because of the severe restrictions it places on monitoring, but it may be worth experimenting all the same — one very well known recording engineer positions the vocalist's microphone in the control room exactly halfway between the main monitors. The cue mix is then replayed over the monitors, but out of phase so that the monitor sound cancels when it reaches the microphone, leaving just the required vocals. This technique is claimed to provide complete freedom from headphones and improved communication between singer and producer; but when I tried it, the monitor mix spill varied in level as the singer moved about and the out‑of‑phase sounds made us all feel horribly ill.
Choosing Microphones
If you intend to record the vocals in concert with the rest of the band, you will have to adopt a close microphone technique simply to get some degree of separation. This will generally force you to use a microphone with a cardioid or hyper‑cardioid polar pattern, a very effective pop‑shield, and a bass filter to minimise the boominess caused by the proximity effect. The end results often tend to sound rather nasal, with all the characteristics associated with close mics. Of course, this may be appropriate to the style of the music, but in most cases a more natural and open sound quality is required.
If you are recording the vocals by themselves as an overdub to previously recorded backings, the options become significantly wider: personal taste (and budgetary constraints) play the major part in the decision over which microphone to use. For this purpose, a large‑diaphragm capacitor microphone is generally hard to beat for overall sound quality and accuracy, but one essential feature it must have is flat frequency response — peaks in the mid or high regions are likely to cause problems with sibilance; premature bass roll‑off will make the vocalist sound thin and weak. Typically, large‑diaphragm capacitor microphones such as the Neumann U87, U47 or TLM170 or the AKG C414 are most commonly used for vocal work, but every manufacturer has a perfectly suitable microphone or two in their range somewhere.
Many engineers prefer the sound of microphones that use valve head‑amps rather than more modern solid‑state designs. Valve microphones not only feel warm to the touch, but they also sound 'warm' and usually have a very flattering quality which suits a number of instruments, and especially voices. Although secondhand vintage valve mics tend to be rather rare, several manufacturers make modern valve microphones which sound extremely good — the Rode Classic, for example.
Positioning
Like virtually every other instrument, the human voice sounds better when recorded from a distance rather than close in. Recording the voice in isolation means that you don't have to bother about achieving good separation, so a minimum voice‑to‑microphone distance might be about 20cm, with a maximum (depending on studio acoustics) of something like 60cm. At these kinds of distances, the recorded voice sounds far more natural and better balanced than anything that can be achieved with close microphone techniques — in particular, breathing and lip noises have a more acceptable perspective. It also means that any small physical movements the singer makes towards or away from the microphone will not cause serious changes in level.
The choice of polar pattern is entirely dependent on the acoustics of the recording studio — an omni‑directional pattern will capture more of the room ambience than a cardioid, of course. If you are recording backing vocals, it may be a good idea to use an omni‑directional microphone anyway so that several singers can gather around it at the same time; this often gives better results than trying to control and balance multiple microphones.
The height of the microphone is important. It is almost impossible to sing properly if you are sitting down or slouched over, so mounting the microphone at, or slightly above, head height will tend to encourage the performer to stand up straight, thereby improving their breathing and projection. Mounting the microphone high also makes it impossible for the singer to get too close and so helps avoid problems with plosives.
If the vocalist is used to stage work, they will probably expect to sing with their lips touching the microphone, which is not what's required in a studio situation. Even if you explain that they should stay a foot or so away, they will often creep in towards the mic over successive takes until they are slobbering all over the thing. Mounting the microphone on a high stand out of reach may effect a cure, or you could try putting up two microphones — one for them to eat, and a more distant one to capture the performance at a more appropriate distance.
The lyric sheet can often be the source of undesirable early reflections, which tend to introduce a coloured or phasey quality to the recording of a solo vocalist. Try to position the paper (and its music stand, if used) so that it will reflect the voice away from the microphone rather than onto it, but beware of placing it in such a way that the performer will be moving their head between reading the lyrics and singing to the microphone.
Dynamic Range
The human voice has a surprising range of dynamics which you'll normally need to reduce considerably to avoid its drowning out the backing instrumentation one moment and becoming lost in the mix the next. Once again, a good vocal technique is an enormous advantage here — the singer should back away from the microphone on loud sections and come in closer on quieter ones. With the advent of decent compressors, a good technique is less critical than it used to be and so few modern singers seem to bother, but most of the more senior vocalists still exhibit the technique — and sound all the better for it!
Trying to follow and control a singer's dynamics on the faders is a recipe for disaster in most cases, and the use of a decent compressor is really mandatory. The settings applied to the compressor will have profound effects on the end result and should ideally be chosen during the mixdown process, when decisions can be made about how the voice should balance with the complete backing tracks, rather than at the recording stage. In other words, avoid compressing the vocal to tape if possible — something which is easier to do with digital recording formats than with analogue ones.
The compression ratio will be determined by the amount of 'squash' needed, but is likely to be something between 2:1 and 5:1. Never use a limiter for vocals and avoid going any higher than 5:1 on a compressor, otherwise the sound will begin to take on a most unpleasant 'hard' or aggressive quality. Using a very low threshold will increase the degree of compression, but the unwanted audible side‑effects of dynamic control will tend to be less obvious. Unfortunately this approach will also require more make‑up gain to restore peak levels, which will introduce more background ambience and tape noise. Ho hum... life is full of compromises. It is not unusual (although arguably undesirable) to require as much as 30‑40dB of gain reduction on really loud vocal peaks with some singers, so choose a compressor that can handle this kind of range (many can barely provide 20dB of gain reduction without sounding unpleasant) and always allow plenty of headroom during the recording.
The compressor's attack time is not usually too critical, but the release time certainly will be, and it should be determined by careful listening. Too fast and the background ambience or tape noise may audibly pump; too slow and the vocals may become rather lifeless and lack sufficient dynamic control. Most compressors have an Auto setting which changes the release time constants automatically to suit the nature of the audio signal from moment to moment. This kind of facility usually works very well and is certainly worth trying.
Cue Mixes
The vocalist will obviously need to hear the backing tracks, but this is another necessity that can adversely affect the end results. Normal practice is to feed a cue mix of off‑tape tracks, plus the vocalist's own microphone, to a pair of headphones in the studio. However, the balance of individual instruments with the performer's own voice is quite critical, poor balances affecting timing, pitch, and dynamics. It is well worth taking as much care over balancing a cue mix as you would with your own monitor mix, although bear in mind that the requirements for a headphone feed are rather different!
Depending on the singer, you may find it useful to restrict the cue mix to a single pitched instrument — a piano or keyboard, say — as this will help the singer to pitch more accurately; on a strongly rhythmic track, the snare or bass drum may have to be quite dominant to ensure good timing from the singer.
I prefer to send the uncompressed voice to the cue mix as I find that this tends to encourage the vocalist to control their own dynamics and places fewer demands on compression for the subsequent mixdown.
One essential requirement for the cue mix is vocal reverb. It is surprising how many mixers make it awkward to send a reverb return to the headphones, but it is a very important facility. Reverb plays a key role in helping singers to pitch correctly, as well as making them feel good about their voices.
Some performers simply cannot work well with headphones, and in these cases pushing one ear‑piece back so that they hear their own voice naturally in the studio acoustic can be a very good idea. The problem to watch out for, however, is cue‑mix spill from the unused ear‑piece getting onto the vocal track. I used to use a special in‑line plug and socket which disabled one side of the headphones, but these days I find it easier to kill one channel of a stereo cue mix (assuming the mixer is suitably equipped). On the subject of spill, make sure that all the other foldback headphones in the studio are turned off during the vocal overdubs too.
Roundup
A good vocal recording relies mainly on three things: good vocal technique; good microphone technique; and good interpersonal skills. The last is probably the most important because the singer will feel far more exposed than other musicians and will consequently need more nurturing and support. Every singer is different and will need to be treated differently — whether we're talking about setting an appropriate mood in the studio, balancing a cue mix or deciding whether or not to try for just one more take — so sensitivity is a valuable commodity.
Listen carefully to the recording and don't be tempted to throw technology at a problem before you have tried more fundamental remedies such as moving the microphone. Use the best‑quality mic you have, with the best microphone preamp, and don't use equalisation unless you really have to. Take your time setting up the compressor and always make decisions about EQ and compression within the context of the complete mix — soloing an instrument does not reflect its character and weaknesses in the same way.
Minding Your 'P'S And 'S'S
Plosive popping on the 'p's, 'b's and 't's of words is caused by high‑velocity puffs of air emitted from the mouth when it creates these sounds, which force the microphone diaphragm to hit its end stops. This is a very common problem in vocal recording, but can easily be cured by a combination of vocal technique and microphone positioning — although it is always best to cure the problem rather than treat the symptom, which means not producing the plosive blasts in the first place. Vocal training can help a lot, as can some effort from an untrained singer to slightly reduce their emphasis on such words. Positioning the microphone slightly to the side of (or, even better, above) the line of frontal projection can also help considerably and it's a very good idea to use a windshield so that any blasts that do reach the microphone are dissipated. Open‑cell foam windshields are supplied with most microphones and work reasonably well — especially if you leave a small air pocket between the windshield and the microphone grille (I don't understand the physics of this, but it seems that the larger the pocket of still air, the better the pop rejection).
An alternative technique, and one which also helps to keep singers at a sensible distance from the microphone, is a separate mesh‑type pop shield mounted on a long gooseneck from the microphone, or perhaps on a separate stand. Several microphone manufacturers make suitable devices (for example the Beyer PS740 or the Sennheiser MZP40 — available from Canford Audio, 0191 415 0205, for about £45 each), but you can make your own quite easily from a circular wire frame supporting a couple of layers of nylon stockings. The frame needs to be between 8‑10cm in diameter and placed about 5cm from the microphone grille in such a position that wind blasts cannot reach the diaphragm. You can easily check the performance of a home‑made mesh by feeling for plosive blasts with the back of your hand. You may need to experiment with the denier rating of the stockings and the number of layers to achieve the best results, but I'm sure you'll enjoy the challenge...
Sibilance is the result of over‑emphasised 's' or 'sh' sounds, and may be caused by the performer's technique, by the poor choice or placing of the microphone, by inappropriate equalisation, or by a lack of headroom in the recording chain. Again, a good vocal technique is the key to an easy life, but there are some things that can be done with technology too.
The choice of microphone is paramount — avoid anything which has even the most gentle of 'presence' peaks. Since high‑frequency sounds tend to beam, positioning the microphone slightly above or to the side of the mouth (much the same as when you're coping with plosives, in fact) will help considerably. Some modest equalisation in the 5‑10kHz region will usually help to reduce the prominence of sibilance, although it can never be removed completely.
Frequency‑selective compression can also be helpful if it's used carefully, but can do more harm then good in the wrong hands. Inserting an equaliser into the sidechain of a compressor, and setting it to provide a mild boost in the 5‑10kHz region, will encourage the compressor to introduce a greater degree of dynamic control to sibilant sounds. Although this technique can produce some very good results, it is often fiddly and time‑consuming to set up and, given a choice, I would recommend using specialist de‑essers which are far easier to 'tune in' quickly.
Finally, never skimp on headroom! A vocalist can have an enormous dynamic range (see below) and sibilance is very good at using up headroom very quickly. Although it is unlikely to be a problem on most modern formats, the pre‑emphasis used in older digital recorders (such as the old PCM701 or F1 systems) reduced headroom at high frequencies, making sibilance a real problem. For similar reasons, analogue recorders that are incorrectly under‑biased will tend to have excessive problems with sibilance.